于 2011年03月31日 01:11, Eric Blake 写道:
On 03/30/2011 07:39 AM, Osier Yang wrote:
Hi, All
I'm thinking to introduce a new flag (something like --remove-disks, --wipe-disks) for "virsh undefine", so that the user can choose whether to remove/wipe the disk devices or not, have seen this requirement in many places, @libvirt-users, public #virt, and also we have a bug of this function. So, IMHO this is a reasonable requirement, following is the rough thoughts:
I'm debating whether delete and wipe as two separate options make sense, or whether we only need one option. I guess for file-based volumes, there is a difference between leaving a wiped file behind and deleting the file altogether;
yes, for fs pool based volumes, they are different. So I guess some user will require both of them. but for most other volume types, wiping is the only
option.
1) General idea. As we don't have a API which can get all the disk devices of a domain, perhaps need to write functions to parse domain xml to extract the disks' path (this is annoyed, but seems don't other way), and then lookup them by storage volume API (virStorageVolLookupByPath), and then can remove or wipe the volume by (virStorageVolDelete/virStorageVolWipe).
virt-manager has a gui option for deleting disks when deleting a domain; it achieves this by making multiple underlying API calls. You may want to use that implementation an example for a starting point. But it also has the advantage of listing all disks associated with the VM, and allowing fine-grain control over which volumes to keep or delete, whereas with virsh, it seems like a new --wipe-disks option would be all or none.
Yes, it has dialog box which can ask user to choose. But for virsh, don't think ask user interactively is a good idea. :-)
At any rate, I think that this is all at the virsh level, and doesn't need any new API additions in include/libvirt/libvirt.h.in.
And for the disk path which doesn't belong to any storage pool, simply remove it by "unlink()"?
No, better would be to error out for any detected disk that cannot be resolved to a volume in a storage pool.
2) Which type of devices can not be removed/wiped.
* Can't delete/wipe ISCSI/SCSI vol.
Can't delete, but can wipe.
* Vol doesn't exists (which will throw an warning when do virStorageVolLookupByPath).
Can we tell the difference between a volume where the backing storage is located within an existing storage pool but the volume has already been deleted prior to deleting the guest XML, and the case of a guest XML that references a disk that does not belong to a storage pool?
In the former case, requesting delete or wipe
* Have no write permission on the parent directory of the disk path. * Can't delete/wipe the disk device which is passthrough'ed from host, (e.g. /dev/sr0 as a CDROM device for guest)
/dev/sr0 would typically be a read-only volume. But I don't see why you can't wipe a read-write device passed through from the host (such as /dev/sda2).
* The storage pool which the disk device belongs to as a vol is marked as "share" * The storage pool which the disk device belongs as a vol is readonly * can't delete disk device of network type. * Any others?
For these situations, we need to do checking and throw straightforward warnings to tell user why it can't be removed/wiped.
Any idea is welcomed. Thanks.
Certainly post-0.9.0, whatever we come up with :)